Base on the topic, I think Fear and Creed index are sentiments tools that describes the current mood in the market as emotion. It is generally accepted that emotional and psychological factors significantly influence trading/investing. A high level of fear will result in coin/token being sold off too cheap, while a extreme greed will cause over valuations over times.
Honestly, I think that greed is more dangerous than fear, because, as we may know, often greed has been condemned as being immoral, sinful, or outright evil across cultures and believe in different parts of the world. In facts, nobody will liketob be called a greedy person in the society,